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question:2. Given two linear functions f(x) and g(x) such that the graphs y=f(x) and y=g(x) are parallel lines, not parallel to the coordinate axes. It is known that the graph of the function y=(f(x))^{2} touches the graph of the function y=11 g(x). Find all values of A such that the graph of the function y=(g(x))^{2} touches the graph of the function y=A f(x).

answer:Answer: A=-11, A=0.Solution. Let f(x)=a x+b, g(x)=a x+c, where a neq 0. The tangency of the graphs y=(f(x))^{2} and y=11 g(x) is equivalent to the equation (f(x))^{2}=11 g(x) having exactly one solution. We get (a x+b)^{2}=11(a x+c), a^{2} x^{2}+a(2 b-11) x+b^{2}-11 c=0. The discriminant of this equation is a^{2}(2 b-11)^{2}-4 a^{2}left(b^{2}-11 cright)=11 a^{2}(11-4 b+4 c), from which 4 b-4 c=11.Similarly, the tangency of the graphs y=(g(x))^{2} and y=A f(x) means that the equation (g(x))^{2}=A f(x) has a unique solution. This equation is equivalent to the following: (a x+c)^{2}=A(a x+b), a^{2} x^{2}+a(2 c-A) x+c^{2}-A b=0. The discriminant is D=a^{2}(2 c-A)^{2}-4 a^{2}left(c^{2}-A bright)=a^{2} A(A- 4 c+4 b). It becomes zero when A=0 and A=4 c-4 b=-11.

question:1. (7 points) The numerator and denominator of the fraction are positive numbers. The numerator was increased by 1, and the denominator by 100. Can the resulting fraction be greater than the original?

answer:Answer: Yes.Solution. For example, frac{1}{200}<frac{2}{300}. There are many other examples.Criteria. Any correct example: 7 points.Answer without an example or incorrect answer: 0 points.

question:On a piece of paper, we can read the following 100 statements:1. On this piece of paper, exactly one statement is false. 2. On this piece of paper, exactly two statements are false.2. On this piece of paper, exactly three statements are false. .3. On this piece of paper, exactly 100 statements are false.Determine which statements are true on the paper.

answer:Among the statements on the paper, any two contradict each other, so at most one statement can be true. The 100th statement cannot be true, because otherwise it would contradict itself. If the 100th statement is false, then there is a true statement among the statements, so according to our previous remark, there is exactly one true statement, and the other 99 are false. It is precisely this fact that the 99th statement records, so among the statements on the paper, the 99th statement is true, and the rest are false.

question:7. mathbf{C 1} (COL) Let A=left(a_{1}, a_{2}, ldots, a_{2001}right) be a sequence of positive integers. Let m be the number of 3-element subsequences left(a_{i}, a_{j}, a_{k}right) with 1 leq i< j<k leq 2001 such that a_{j}=a_{i}+1 and a_{k}=a_{j}+1. Considering all such sequences A, find the greatest value of m.

answer:7. It is evident that arranging of A in increasing order does not diminish m. Thus we can assume that A is nondecreasing. Assume w.l.o.g. that a_{1}=1, and let b_{i} be the number of elements of A that are equal to i left(1 leq i leq n=a_{2001}right). Then we have b_{1}+b_{2}+cdots+b_{n}=2001 and m=b_{1} b_{2} b_{3}+b_{2} b_{3} b_{4}+cdots+b_{n-2} b_{n-1} b_{n} Now if b_{i}, b_{j}(i<j) are two largest b's, we deduce from (1) and the AMGM inequality that m leq b_{i} b_{j}left(b_{1}+cdots+b_{i-1}+b_{i+1}+cdots+b_{j-1}+b_{j+1}+b_{n}right) leq left(frac{2001}{3}right)^{3}=667^{3} quadleft(b_{1} b_{2} b_{3} leq b_{1} b_{i} b_{j}right., etc.). The value 667^{3} is attained for b_{1}=b_{2}=b_{3}=667 (i.e., a_{1}=cdots=a_{667}=1, a_{668}=cdots=a_{1334}=2, a_{1335}=cdots=a_{2001}=3 ). Hence the maximum of m is 667^{3}.

question:Which of the following statements regarding a bijection from set A to set B is correct? (  )1. A bijection is also called a one-to-one correspondence.2. Different elements in set A have different images in set B.3. Every element in set B has a preimage in set A.4. The set of images is exactly set B.A: 1, 2B: 1, 2, 3C: 2, 3, 4D: 1, 2, 3, 4

answer:According to the concept of mapping:- A bijection is also referred to as a one-to-one correspondence, which is correct.- Since a bijection is injective, different elements in set A have different images in set B.- Since a bijection is surjective, every element in set B has a preimage in set A.- The set of images is the same as set B because a bijection is both injective and surjective.Therefore, the correct option is boxed{D}.A mapping that is both injective and surjective is called a bijection, which is also known as a one-to-one correspondence. This allows us to confirm options 1, 2, 3, and 4.This question examines the concept of a bijection and is considered a fundamental problem.

question:11. In the diagram, lines Q T and R S are parallel and P Q and Q T are equal. Angle S T Q is 154^{circ}. What is the size of angle S R Q ?A 120^{circ}B 122^{circ}C 124^{circ}D 126^{circ}E 128^{circ}

answer:SolutionESince angle S T Q=154^{circ} and angles on a straight line add to 180^{circ}, angle P T Q=26^{circ}. Hence, since P Q and Q T are equal, triangle P T Q is isosceles and so angle T P Q=26^{circ}. Therefore, since angles in a triangle add to 180^{circ}, angle T Q P=128^{circ}. Finally, since Q T and R S are parallel and corresponding angles on parallel lines are equal, angle S R Q=128^{circ}.

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